docs: def conceptual_info(subsystem):
      """Return the conceptual information for a |Subsystem|.
  
      This is the distance from the subsystem's |CauseEffectStructure| to the
      null concept.
      """
      ci = ces_distance(ces(subsystem),
                        CauseEffectStructure((), subsystem=subsystem))
      return round(ci, config.PRECISION)